The walls of an insulated lunch box are made of inch-thick styrofoam with a thermal conductivity of 0.05W/m*K. If an ice cube, one inch on a side, is placed in the box and the box placed in an ambient medium at 90F with an external heat transfer coefficient of h=10W/m^2K, how long is required for half the ice cube to melt? State clearly all the assumptions you make in formulating your model of this problem.